We present a case of a 44-year-old female with fluctuating thyroid function over 12-14 years. The patient originally presented with a high TSH, normal free T3/T4 and a negative anti-TPO antibody. She was initially monitored, then went onto Levothyroxine replacement in an antenatal setting. Subsequently, 12-18 months later, she presented with hyperthyroid symptoms and vastly elevated TSH-receptor-antibody (TSHR-ab) titre of >10 IU/L, the upper limit of normal being 2.9 IU/L. She was commenced on Carbimazole, with this continuing for 4-years. We have observed a fluctuating thyroid profile and antibody profile, over a 12-14 year period and treatment with Levothyroxine followed by Carbimazole in the same patient. We note that prior to 2018, TSHR-ab assessment was not widely available. This case highlights the fluctuating nature of TSHR-ab titre related symptoms, as interestingly, the same patient displayed both underactive and overactive thyroid physiology over a 12-year period. Her TSH fluctuated between 13.6 to 0.01 mU/L 10-12 years prior to the initiation of Levothyroxine. Symptoms also fluctuated and so the patient was monitored and not treated, this decision being supported by a negative TPO-antibody titre. There was thought that this could have been sub-acute thyroiditis or sub-clinical presentation. The patient was monitored and as TFT did return to normal range, the patient was discharged. After a period of observation, she presented in florid hyper-thyroid phase finally with very high TSHR-ab titre. According to the American Thyroid Association statement (1), the severity of symptoms are proportional to the amount of anti-body titre, as noted in this case. There was no overlap with TPO-antibody titre, as this patients TPO-antibody titre was normal. This prompted another endocrinologist to monitor and not treat the fluctuating TFTs, and this remained the case for some time till final presentation with florid symptoms, high Free T4/ T3 and suppressed TSH.
References: 1. Ross DS, Burch HB, Cooper DS, Greenlee MC, Laurberg P, Maia AL, et al. 2016. American Thyroid Association guidelines for diagnosis and management of hyperthyroidism and other causes of thyrotoxicosis. Thyroid (2016) 26(10):1343421. 10.1089/thy.2016.0229